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Monday, March 30, 2015

Tendon Boots and Temperature

The application of bandages and tendon boots to the lower limb of horses is widespread and performed for many reasons. Tendon boots are used in training and are applied during some horse competitions. Bandages and tendon boots are supposed to support the anatomic structures, reduce the maximum extension of the fetlock joints and protect the limbs from fractures and trauma; however, there is little scientific data to support their value except in protection against direct trauma.

The objective of this research, conducted by researchers in Austria, was to determine the skin temperature of the cannon bone in horses associated with the use of bandages and tendon boots, compared with the bare limb, at rest and after 20 minutes of lunging.

Skin temperatures at rest were not different with a bare limb, bandage, or tendon boot. Average skin temperatures ranged from 57 to 59°F. Skin temperate of the bare cannon bone after exercise did not increase and remained at 57°F. Skin temperature of the cannon bone in horses increased during exercise when a bandage or tendon boot was used. Skin temperatures under the bandage and tendon boot were 77°F and 70°F, respectively, after exercise.

The authors speculate that both a bandage and a tendon boot accelerate the warmup phase of exercise by increasing the skin temperature. Moderate warmup exercise increases blood flow in tissues, which can help to reduce the risk of injuries. It is not known whether heavy exercise performed with limb bandages or tendon boots is detrimental because of accumulation of heat in the limb and underlying structures. Further research should focus on the effects of warmup and maximum exercise on the temperature of other anatomic structures such as tendons.

For more information, click here. Summarized by: Krishona Martinson, PhD, University of Minnesota.

Selenium Toxicity

Horses are very susceptible to chronic selenium toxicity (selenosis) if grazed on forages grown on high selenium soils for prolonged periods. Selenium toxicity from soils is mostly an issue in the Western U.S.; however, horses on multiple supplements containing selenium can be affected by selenium toxicity. Clinical signs of selenium toxicity include dysplastic or corrugated hoof lesions (see photo), dull hair coat, mane and tail alopecia, and varying lameness with severe cases resulting in untreatable hoof necrosis and sloughing resulting in euthanasia. In this study, conducted by researchers in Utah, mane and tail samples from horses that exhibited classical hoof lesions of chronic selenosis were analyzed.

The horses had grazed for 6 months, from approximately May 15 until November 15, each year for three grazing seasons in a pasture containing forage and water sources with elevated selenium concentrations.

The segmented hair samples showed a cyclic pattern in selenium concentrations in the mane and tail, which corresponded to entering and exiting the contaminated pasture. The selenium concentration in the tail of one horse could be traced for three grazing seasons.

These results demonstrate that in some cases, hair samples can be used to determine selenium exposure in horses for up to 3 years post-exposure. For more information, click here.

Summarized by Krishona Martinson, PhD, University of Minnesota

Magnetic Blankets

Static magnetic blankets often claim to increase blood flow, reduce muscle tension and tenderness, and be beneficial in both prevention and treatment of musculoskeletal injuries in horses. However, there are no studies that confirm the beneficial effects of magnets on muscles of the back in healthy horses.

Research in Sweden set out to investigate whether static magnets sewn into a blanket affect back muscle blood flow, skin temperature, mechanical nociceptive threshold and behavior in healthy horses.

Ten healthy adult horses were evaluated for blood flow by photoplethysmography, skin temperature by use of thermistors in conjunction with digital infrared thermography, and mechanical nociceptive threshold by algometry. Horse behavior was filmed during the procedure and scored on an ethogram. Measurements were performed repeatedly for 30 minutes to establish a baseline. Thereafter, a blanket with active, static magnets (900 gauss) or placebo magnets was placed on the horse and measurements were performed for a 60 minute treatment period and a 30 minute post treatment period.

Blood flow in muscle, skin temperatures, mechanical nociceptive thresholds and behavioral traits did not differ between active and placebo magnetic blankets. Skin temperature increased similarly during both active and placebo blanket treatment.

 In healthy horses, magnetic blankets did not induce additional effects on muscle blood flow, skin temperature, mechanical nociceptive threshold and behavior when compared with nonmagnetic blankets.

For more information on this research, click here.  Summarized by: Krishona Martinson, PhD, University of Minnesota

Bedding Materials

It can be a challenge to find suitable horse bedding materials that provide higher moisture absorption, acceptable animal comfort, good fertilizer values, and improve indoor environmental quality.

 Researchers at North Dakota State University set out to determine the water absorption capacity of two bedding materials, flax shive (a newer bedding material) and pine wood shavings which are commonly used by equine facilities. The second objective was to measure ammonia, hydrogen sulfide, and greenhouse gas concentrations emitted from stall surfaces bedded with both materials. 

 The water absorption capacity of bedding materials were measured at 0.5, 1, 2, 3, 4, 6, 8, 12, and 24 hours in a laboratory. A total of eight horses were used for a 14-day study period. Of these, four horses were bedded with flax shive and the other four were bedded with pine wood shavings for week 1. During week 2, the bedding materials were switched between the two groups. Ammonia and hydrogen sulfide were measured in the stalls. Greenhouse gas measurements were collected 6 inches above the bedded stall surface.

The size of pine wood shavings were much larger than flax shive. The smaller particle size might be a precursor of dust, which was noticed in the stalls bedded with flax shive. The water absorption capacity of flax shive was 56% greater than the pine wood shavings when soaked for 24 hours. There were no differences in ammonia, hydrogen sulfide, and greenhouse gas concentrations between the two bedding materials. Mean nutrient content was similar between both fresh bedding materials, except for phosphorous and potassium. As expected (due to the addition of manure and urine), the nutrient content between fresh and soiled bedded samples for each bedding material were different. Total phosphorus and potassium contents of soiled pine wood shavings bedding were approximately 7 and 20 times higher, respectively, than those of fresh pine wood shavings bedding material. Total nitrogen and total phosphorous contents of bedded flax shive were approximately twice than those of fresh flax shive.  

Flax shive shows potential as a new bedding source for use in horse stalls. For more information, click here

 Summarized by: Krishona Martinson, PhD, University of Minnesota.

Managing Laminitis

Excessive bodyweight has become a major health issue in the equine industry. Obesity can contribute to other diseases, including Equine Metabolic Syndrome, laminitis and insulin resistance. Therefore, researchers from Auburn University recently explored methods of rehabilitation used to manage obese horses with laminitis.

 Clinical data from 14 similar laminitis cases were analyzed to evaluate responses to rehabilitation after 5 to 20 months of treatment. Each horse presented as obese and laminitic with no history of a systemic inflammatory disease. The rehabilitation method emphasized a mineral-balanced, low nonstructural carbohydrate diet; daily exercise; hoof trimming that minimized hoof wall loading; and sole protection in the form of rubber hoof boots and/or hoof casts.

 Coffin bone (distal phalanx) alignment within the hoof capsule was improved, and hoof wall thickness was decreased following treatment. Solar depth was also increased. Reduction of heel (palmar) angle measurements was detected in acutely and chronically affected horses. This treatment effect was greater for horses with chronic laminitis than for horses with acute laminitis. Horses were 5.5 times more likely to be sound post-treatment than before treatment.

 Daily exercise, dietary modification, and removal of ground reaction force from the hoof wall were focuses of the rehabilitation program. Hoof care and husbandry as applied to these horses may be an effective method of rehabilitation of horses from obesity-associated laminitis.

 Summarized by Krishona Martinson, PhD, University of Minnesota.

Weeds Commonly Found in Drylots

Laminitis (or founder) is a devastating, painful condition for horses leading to losses in performance, increased veterinary costs, and even death. Diets high in nonstructural carbohydrates are a known trigger for laminitis. Horses that are easy keepers, or overweight, are also at a greater risk of developing laminitis and tend to be classified as having equine metabolic syndrome. Some of the most effective management tools for horses prone to laminitis are to limit their nonstructural carbohydrate intake by testing forage for nonstructural carbohydrate content, restricting amounts of feed to encourage weight loss, and confining to dry lots (i.e. dirt paddocks) in order to avoid access to pasture grasses that are commonly high in nonstructural carbohydrates and digestible energy (i.e. calories).   

Researchers have recommended a total diet (i.e. hay, grain, supplements, treats) of less than 12% nonstructural carbohydrates for horses diagnosed with laminitis or equine metabolic syndrome. However, recent reports from horse owners indicate horses housed on dry lots are still experiencing recurring bouts of laminitis, despite being fed a low nonstructural carbohydrate diet. Weeds that commonly grow in dry lots may be both palatable to horses and high in nonstructural carbohydrates; therefore, capable of triggering a laminitis episode. The objective of this research, conducted at the Univ. of Minn., was to determine nonstructural carbohydrate content of weeds commonly found in dry lots housing horses or ponies with a history of laminitis.   

During the summer of 2013, 10 farms in Minnesota and Wisconsin were visited three times (spring, summer and fall), and up to four weeds growing in dry lots housing laminitic horses or ponies were collected. Samples were sent to a forage testing laboratory and analyzed.    

Twenty-seven different weed species were collected. The 6 most common weed species included prostrate knotweed, plantain, redroot pigweed, common ragweed, cinquefoil, and purslane. The average nonstructural carbohydrate content of the weed species varied with plantain have the highest and prostrate knotweed the lowest. There were no differences in nonstructural carbohydrate content within weed species across farms; however, nonstructural carbohydrate content was higher during the fall. It is common for plants to have higher nonstructural carbohydrate contents in the fall due to weather conditions. Most plants continually produce nonstructural carbohydrates during the day and utilize them at night. However, plants essential shut down during cool nights and therefore do not utilize nonstructural carbohydrates which contribute to higher levels commonly observed in the fall.

The average nonstructural carbohydrate content of plantain, cinquefoil and ragweed was greater than the maximum 12% total diet recommendation for horses diagnosed with laminitis or equine metabolic syndrome. However, the maximum amount of nonstructural carbohydrate content exceeded this recommendation for all weed species. Nutritive analysis of other components indicated the weeds would be palatable to most horses, especially ones housed in a dry lot on a restricted diet (i.e. horses who might feel hungry). All weed species were relatively low in structural carbohydrate components and high in crude protein. Combined, these results have proven to increase palatability; therefore, it is not surprising the horses consumed the weeds. 

 Although this research did not directly link the ingestion of weeds to laminitis, the wide range of nonstructural carbohydrate content within the weed species suggests horse owners should control weeds in dry lots, especially if used to house laminitic horses and ponies.  

This project was sponsored by a grant from the Minnesota Horse Council. Authors: D. Gunder and K. Martinson, PhD, Univ. of Minn. and J. Wilson, DVM, MN Board of Vet Med.


Bodyweight Estimation

Excessive bodyweight has become a major health issue in the equine industry. The objectives of the study, conducted at he University of Minnesota, were to determine if the addition of neck circumference and height improved existing bodyweight estimation equations; develop an equation for estimation of ideal bodyweight; and develop a method for assessing the likelihood of being overweight in adult equines.

In 2011, 629 adult horses and ponies were measured and weighed at two horse shows in Minnesota (WSCA Champ Show and State 4-H Horse Show). Personnel assessed body condition score (BCS) on a scale of 1 to 9, measured wither height, body length from the point of shoulder to the point of the buttock, neck and girth circumference, and bodyweight using a livestock scale. Individuals were grouped into breed types and equations for estimated and ideal bodyweight were developed. For estimated body weight, the model was fit using all individual equines. For ideal bodyweight, the model was fit using only individuals with BCS of 5. Breed type, height and body length were also considered as these measurements are not affected by fat deposits. Finally, a bodyweight score to assess the likelihood of being overweight was developed and standardized using horses with a BCS of 5.
Breed types included Arabian, stock and pony. Mean BCS was 5.6.  Bodyweight (lbs) was estimated by taking girth (in)1.486 x length (in)0.554 x height (in)0.599 x neck (in)0.173/119 (Arabians), 119 (ponies) or 114 (stock horses). Ideal body weight (lbs) was estimated by taking length (in) x 15.65 + height (in) x 23.47 – 1,344 (Arabians), 1,269 (ponies) or 1,333 (stock horses).
Equines with a BCS of ≥ 7 had a greater likelihood of being overweight and the model suggested cutoffs at the 48th and 83rd percentiles for underweight and overweight horses, respectively. In conclusion, body measurements were successfully used to develop equine bodyweight-related equations.

To encourage use of the equations, the research team developed a mobile app for Apple and Android operating systems. Users enter the body measurements and the app calculates estimated and ideal bodyweight and a bodyweight score.

 Information on the “Healthy Horse” app can be found here.   For more information on this research, click here

 Summarized by Krishona Martinson, PhD, University of Minnesota
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